U.S. patent application number 15/939285 was filed with the patent office on 2018-10-11 for light-guide optical element and method of its manufacture.
The applicant listed for this patent is LUMUS LTD. Invention is credited to Meir Tzion Bitan, Edgar Friedmann, Yuval OFIR.
Application Number | 20180292599 15/939285 |
Document ID | / |
Family ID | 61906644 |
Filed Date | 2018-10-11 |
United States Patent
Application |
20180292599 |
Kind Code |
A1 |
OFIR; Yuval ; et
al. |
October 11, 2018 |
LIGHT-GUIDE OPTICAL ELEMENT AND METHOD OF ITS MANUFACTURE
Abstract
An optical structure and corresponding process of manufacture
for light guide optical elements (LOEs) which guide light by
reflection at major surfaces. The structure further includes light
directing surfaces for coupling light out of the LOE, obliquely
inclined with respect to the major surfaces. The optical structure
is formed from a stack of multiple optically transparent layers
each of which has a surface pattern of regions configured as light
directing surfaces which are arranged in an X-Z plane in a
spaced-apart relationship along at least the X-axis with optically
transparent regions between them. The layers are stacked along a
Y-axis so that each of the surface patterns is located at an
interface between two adjacent layers and the patterns of the
layers are aligned with a shift of a predetermined value along one
or both of the X-axis and Z-axis.
Inventors: |
OFIR; Yuval; (Ness Ziona,
IL) ; Friedmann; Edgar; (Ness Ziona, IL) ;
Bitan; Meir Tzion; (Ness Ziona, IL) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
LUMUS LTD |
Ness Ziona |
|
IL |
|
|
Family ID: |
61906644 |
Appl. No.: |
15/939285 |
Filed: |
March 29, 2018 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G02B 27/0172 20130101;
G02B 27/0081 20130101; G02B 6/0065 20130101; G02B 27/145 20130101;
G02B 6/0036 20130101; G02B 6/0055 20130101; G02B 6/0076 20130101;
G02B 27/1073 20130101; G02B 6/0058 20130101 |
International
Class: |
F21V 8/00 20060101
F21V008/00 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 6, 2017 |
IL |
251645 |
Claims
1. An optical structure used for producing therefrom two or more
light guide optical elements (LOEs), configured such that each LOE
comprises an optically transparent body for guiding input light in
a general propagation direction through the body by total internal
reflections of light from major surfaces of the body and comprises
light directing surfaces for coupling the input light out of the
body in one or more output directions, where the light directing
surfaces are fully embedded in a volume of the body being spaced
from the major surfaces of the boy and are inclined with respect to
said major surfaces at a predetermined angle, the optical structure
being configured as a stack of multiple optically transparent
layers, wherein: each of said optically transparent layers has a
surface pattern of parallel regions configured as light directing
surfaces which are arranged in an X-Z plane in a spaced-apart
relationship along at least X-axis with optically transparent space
regions between them; the multiple layers are stacked one on top of
the other along a Y-axis such that each of the surface patterns is
located at an interface between two adjacent layers and the
patterns of said layers are aligned with a shift of a predetermined
value along one of the X-axis and Z-axis; such that the optical
structure can be divided, by spaced-apart parallel dicing planes
intersecting with a X-Z plane and forming a predetermined angle
with the X-Z plane, into a predetermined number of slices spaced
along said one of the X-axis and Z-axis, configured as a plurality
of the optically transparent bodies for the LOE elements, where
each of said bodies has an inner pattern comprising an array of the
light directing surfaces arranged in the spaced-apart, parallel
relationship and being fully embedded in the LOE's body and
inclined with respect to major surfaces of the LOE body, defined by
said dicing planes, with said predetermined angle.
2. The optical structure according to claim 1, wherein the multiple
layers are stacked one on top of the other along the Y-axis with
the shift along said one of the X-axis and Z-axis, thereby
providing that the patterns of said layers are aligned with said
shift.
3. The optical structure according to claim 1, wherein the multiple
layers comprises at least two layers of different thicknesses.
4. The optical structure according to claim 1, wherein said light
directing surfaces of the pattern are arranged in spaced-apart
relationship along the X-axis and Z-axis.
5. The optical structure according to claim 1, wherein said light
directing surfaces comprise surfaces having different optical
properties differently affecting the input light.
6. The optical structure according to claim 1, wherein the light
directing surfaces comprise surfaces directing light by at least
one of reflection and diffraction effects.
7. The optical structure according to claim 1, wherein the patterns
of said layers are aligned with the shift along the X-axis, said
shift being of a value smaller than a minimal space between said
light directing surfaces along the X-axis.
8. The optical structure according to claim 1, wherein the light
directing surfaces comprise surfaces which are substantially
equally spaces from the major surfaces at said dicing planes.
9. The LOE according to claim 1 wherein the light directing
surfaces comprise surfaces of different dimensions such that they
are differently spaces from the major surfaces at said dicing
planes.
10. A method for fabricating two or more light guide optical
elements (LOEs), such that each of said two or more LOEs comprises
an optically transparent body for guiding input light in a general
propagation direction through the body by total internal
reflections of light from major surfaces of the body and comprises
at least one light directing surface for coupling the input light
out of the body in one or more output directions, where said at
least one light directing surface is fully embedded in a volume of
body being spaced from the major surfaces of the body and inclined
with respect to said major surfaces at a predetermined angle, the
method comprising: preparing at least one patterned substrate, the
patterned substrate having an optically transparent planar body
with a surface thereof formed with a pattern of spaced apart,
parallel regions having light directing surfaces, which are
arranged in an X-Z plane in a spaced-apart relationship along one
of X-axis and Z-axis with optically transparent spacer regions of
the substrate between them; enclosing said at least one patterned
substrate between top and bottom optically transparent substrates,
thereby forming a stack of multiple optically transparent layers
stacked one on top of the other along Y-axis, where the pattern of
the spaced apart, parallel, light directing surfaces is located at
an interface between the layers; dicing said stack of multiple
optically transparent layers along a dicing plane intersecting with
an X-Z plane and forming a predetermined angle with said X-Z plane,
into a predetermined number of slices spaced from one another along
said one of the X-axis and Z-axis, to thereby define a plurality of
bodies for the LOEs, each of said bodies comprising the at least
one light directing surface which is fully embedded in the LOE's
body.
11. The method according to claim 10, further comprising applying
edge cutting to each of said slices producing the LOE having the
optically transparent body for guiding input light in a general
propagation direction by total internal reflections from its major
surfaces and comprising the at least one light directing surface
for affecting the input light propagation towards one or more
output directions, which is spaced from the major surfaces.
12. The method according to claim 10, comprising more than one
patterned substrates placed one on top of the other along the
Y-axis and being all enclosed between said top and bottom layers,
such that the patterns of said patterned substrates are located at
interfaces between the adjacent layers and are shifted with respect
to one another along one of X-axis and Z-axis, thereby forming said
plurality of the LOEs, each LOE comprising an inner pattern
comprising two or more spaced-apart light directing surfaces fully
embedded in the body.
13. The method according to claim 10, comprising more than one
patterned substrates placed one on top of the other along the
Y-axis, being all enclosed between said top and bottom layers,
wherein the patterned substrates are shifted with respect to one
another along X-axis, thereby providing that the patterns of said
patterned substrates are shifted with respect to one another along
X-axis with a shift value being smaller than a minimal spacer
region between the adjacent light directing regions in the layer,
thereby forming said plurality of the LOEs, each LOE comprising an
inner pattern comprising two or more spaced-apart light directing
surfaces fully embedded in the body.
14. The method according to claim 10, wherein dimensions of the
spacer regions and the dicing of said stack into the slices defines
distance of the light directing surface from the major surfaces of
the LOE.
15. The method according to claim 12, wherein the two or more light
directing surfaces comprise regions of different dimensions such
that they are differently spaced from the major surfaces.
16. The method according to claim 12, wherein said two or more
light directing surfaces comprise regions having different optical
properties differently affecting the input light.
17. The method according to claim 10, wherein the light directing
surfaces comprise surfaces directing light by at least one of
reflection and diffraction effects.
18. The method according to claim 10, wherein said preparing of the
at least one patterned substrate comprises applying to a surface of
the optically transparent planar body a lithography process to
create said pattern of the spaced apart, parallel, light directing
surfaces spaced by optically transparent spacer regions.
19. The method according to claim 18, wherein said lithography
process is configured to apply a negative or positive patterning to
create said pattern.
20. The method according to claim 10, wherein said preparing of the
at least one patterned substrate comprises applying to a surface of
the optically transparent planar body a direct writing patterning
process to create said pattern of the spaced apart, parallel, light
directing surfaces spaced by the optically transparent spacer
regions.
21. The method according to claim 10, wherein each of the major
surfaces comprises an outer coating including at least one of the
following: Hard Coating (HC), Anti-scratch coating,
super-hydrophobic coating, anti-smudge coating, anti-bacterial and
anti-fouling coating, Anti-reflection coating.
22. The method according to claim 21, comprising applying one of
the following processes to said outer surfaces to create said major
surfaces of the LOE: liquid/solvent based coating; one or more
printing techniques; one or more dry coatings.
23. The method according to claim 22, wherein said liquid/solvent
based coating comprises at least one of the following: dip coating,
spin coating, spray-coating, die coating, capillary coating, roll
coating, curtain/knife coating, bar-coating.
24. The method according to claim 22, wherein said one or more dry
coatings comprise at least one of the following: evaporation; and
sputtering of optical coatings.
25. The method according to claim 22, further comprising applying a
curing processes to the liquid/solvent based coatings or printed
coatings on said outer surfaces.
26. The method according to claim 25, further comprising applying
polishing to the outer surfaces.
27. A light guide optical element (LOE) comprising an optically
transparent body comprising major surfaces and configured for
guiding input light in a general propagation direction through the
body by total internal reflections of light from said major
surfaces, and carrying at least one light directing surface
configured for coupling said input light out of the body towards
one or more output directions and being fully embedded in a volume
of said body such that it is spaced from the major surfaces, the
LOE being manufactured by a method comprising: preparing at least
one patterned substrate having an optically transparent planar body
with a surface thereof formed with a pattern of spaced apart,
parallel, light directing regions, which are arranged in an X-Z
plane in a spaced-apart relationship along one of X-axis and Z-axis
with optically transparent regions of the substrate between them;
enclosing said at least one patterned substrate between top and
bottom optically transparent substrates, thereby forming a stack of
multiple optically transparent layers stacked one on top of the
other along Y-axis, where the pattern of the spaced apart,
parallel, light directing regions is located at an interface
between the layers; dicing said stack of multiple optically
transparent layers along a dicing plane intersecting with an X-Z
plane and forming a predetermined angle with said X-Z plane, into a
predetermined number of slices spaced from one another along said
one of the X-axis and Z-axis, to thereby define a plurality of
bodies for the LOEs, each of said bodies comprising the at least
one light directing region which is fully embedded in the LOE's
body.
Description
TECHNOLOGICAL FIELD AND BACKGROUND
[0001] The present invention is in the field of optical devices and
relates to a compact light-guide optical element and a method of
its manufacture. More specifically, the present invention relates
to a substrate-guided optical device including one or more at least
partially reflecting or diffractive surfaces carried by a common
light-transmissive substrate.
[0002] Such light-guide optical element (LOE) can be used in a
large number of imaging applications, such as portable DVDs,
cellular phone, mobile TV receiver, video games, portable media
players, or any other mobile display devices, e.g. see-through
near-eye display, or head-mounted display, for use in
augmented/virtual reality systems. The main physical principle of
the operation of LOE is that light waves are trapped inside a
substrate by total internal reflections from the major surfaces of
the LOE. In addition, the light waves which are trapped inside the
LOE are coupled out into the eyes of the viewer by one or more
internal reflecting or partially reflecting/diffractive
surfaces.
[0003] One of the important factors defining the performance of the
above-described LOE is associated with a requirement for uniformity
of illumination formed by light output from the LOE. To this end,
the actual active area of each partially reflecting surface is to
be considered, because a potential non-uniformity in the resulting
image might occur due to the different reflection sequences of
different rays that reach each selectively reflecting surfaces.
More specifically, some rays arrive without previous interaction
with a selectively reflecting surface; while other rays arrive
after one or more partial reflections.
[0004] Since the inactive portions of the selectively reflecting
surfaces do not contribute to the coupling of the trapped light
waves out of the substrate, their impact on the optical performance
of the LOE can be only negative. That is, if there is no
overlapping between the reflecting surfaces then there will be
inactive optical portions in the output aperture of the system and
"holes" will exist in the image. On the other hand, the inactive
portions of the reflecting surfaces are certainly active with
respect to the light waves from the external scene. In addition,
the major axis orientation of two adjacent surfaces cannot be
identical; otherwise the entire second surface will be inactive.
Therefore, if overlapping is set between the reflective surfaces to
compensate for the inactive portions in the output aperture then
rays from the output scene that cross these overlapped areas will
suffer from double attenuations and holes will be created in the
external scene. This phenomenon significantly reduces the
performance not only of displays, which are located at a distance
from the eye like head-up displays, but that of near-eye displays
also.
[0005] The above problem, and some solutions therefor, are
described for example in U.S. Pat. No. 7,724,443 and WO
2007/054928, both assigned to the assignee of the present
application. The possible technique to overcome the problem is by
providing that only the actual active portions of the partially
reflecting surfaces are embedded inside the substrate, that is, the
reflecting surfaces do not intersect with the lower major surface,
but terminate short of this surface. Since the ends of the
reflecting surfaces are adjacent to one another over the length of
the LOE, there is no holes in the projected augmented image, and
since there is no overlap between the surfaces there is no holes in
the real image of the external view, thus providing uniform
illumination.
GENERAL DESCRIPTION
[0006] There is need in the art for a novel approach for the
fabrication of light guide elements (LOEs) of the kind described
above, namely LOEs configured for trapping light inside a substrate
by total internal reflections from the major surfaces of the LOE,
and carrying one or more reflecting or partially
reflecting/diffractive surfaces for coupling the trapped light out
of the substrate.
[0007] Such LOE and light propagation scheme therein and out
thereof is generally illustrated in FIG. 1A. The LOE 20 has a light
input region 21 (e.g. being aligned with an output of a virtual
image source), major surfaces 26 and 28 guiding light by total
internal reflections therefrom, and one or more at least partially
reflective/diffractive surfaces 22 arranged with proper orientation
inside the LOE. After several reflections from the major surfaces
26, 28, the trapped light waves reach the selective partially
reflecting surface(s) 22, coupling the light out of the LOE to
propagate in output direction(s) towards a pupil 25 of viewer's eye
24.
[0008] Generally speaking such at least partially
reflective/diffractive surface 22 embedded in the LOE's substrate
serves for redirecting the light propagating in a general
propagation direction through the substrate in one or more output
directions. For simplicity, such surface is termed herein below as
"light directing surface".
[0009] As known, for example from the above-indicated U.S. Pat. No.
7,724,443 and WO 2007/054928 assigned to the assignee of the
present application, the high performance (e.g. uniform
illumination) of the LOE can be provided by embedding such light
directing surfaces 22 in the substrate such that they are spaced
from the major surface(s) 26, 28.
[0010] As schematically shown in FIG. 1B, according to some of the
techniques described in these patent publications, such
configuration can be achieved by attaching a blank plate 132 (i.e.
a plate with no partially reflecting surfaces) to one of the major
surfaces of the light guide substrate 130 (e.g. by using optical
cement), so as to yield at an LOE 134 with the appropriate active
apertures for all of the reflecting surfaces. As noted above, the
two major surfaces, 26 and 28, are parallel to each other in such a
way that the combined structure forms a complete rectangular
parallelepiped.
[0011] As shown schematically in FIG. 1C, according to alternative
techniques known from these patent publications, the same can be
achieved by fabricating two similar, tooth-shaped transparent forms
140 fabricated by injection-molding or casting. The required
reflecting surfaces 22 (either anisotropic or coated thin-film) are
inserted in the appropriate places between the forms 140 and the
two forms are then glued together to create the required LOE
144.
[0012] As seen in the figures, the resulting structure 134 (FIG.
1B) has interface 50 located in a plane parallel to the major
surfaces and thus inclined with respect to the reflecting surfaces
22; and the resulting structure 144 (FIG. 1C) has an interface 150
having regions/segments 150A located in planes substantially
parallel to the reflecting surfaces 22 and regions/segments 150B
located in planes intersecting those of the reflecting surfaces and
the major surfaces.
[0013] Generally, in order to achieve an undistorted image having
good optical quality, the major and the (partially)
reflecting/diffractive surfaces should have high quality. On the
other hand, it is desired that the fabrication process of such LOE
is as simple and straightforward as possible, as well as cost
effective.
[0014] The present invention provides a novel approach for the
fabrication of an LOE with one or more at least partially
reflecting/diffractive surfaces (at times referred to herein below
as "light directing surfaces") coupling light out of the LOE's
substrate/body, and a resulting novel configuration of the LOE.
[0015] Thus, according to one broad aspect of the invention, it
provides a light guide optical element (LOE) comprising: an
optically transparent body which has major surfaces for guiding
input light in a general propagation direction through the body by
total internal reflections of light from said major surfaces, and
carries at least one light directing surface, each light directing
surface being configured for coupling the input light out of the
body towards one or more output directions. The configuration is
such that each of said at least one light directing surface is
fully embedded in a volume of said body such that it is spaced from
the major surfaces; and the body comprises one or more interfaces
inside the body, where all of said one or more interfaces inside
the body are located in at least one plane parallel to each of said
at least one light directing surface and inclined with respect to
said major surfaces at a predetermined angle, said at least one
light directing surface being located in at least one region,
respectively, at one of said one or more interfaces.
[0016] It should be understood, that in the LOE of the invention
there are no interfaces other than those parallel to the light
directing surfaces and extending between the major surfaces, and
all the light directing surfaces are arranged in regions of at
least some of such interfaces. In this connection, it should be
understood that the term "interface" used herein refers to a
physical boundary between elements forming an integral structure of
the LOE.
[0017] In some embodiments, the body (substrate) of the LOE
comprises an inner pattern formed by an array of two or more of the
light directing surfaces arranged in a spaced-apart parallel
relationship along at least one axis. The light directing surfaces
of the array are located at the one or more interfaces inside the
body and are fully embedded in the volume thereof such that the two
or more light directing surfaces are spaced from the major
surfaces.
[0018] At least some of such multiple light directing surfaces may
be substantially equally spaced from the at least one of the major
surfaces; as well as at least some of the multiple light directing
surfaces may be of different or same dimensions, while differently
spaced from the major surfaces.
[0019] It also should be noted that, although the invention is
described below as using light directing surfaces being at least
partially reflective/diffractive with respect to the input light
propagating in the body, the principles of the invention are not
limited to these specific applications. Thus, generally, the light
directing surfaces have optical properties different from their
surroundings, and may generally include surfaces having different
optical properties differently affecting the input light
propagating though the body (e.g. inducing polarization effect,
spectral effect, etc.).
[0020] In some embodiments, the multiple light directing surfaces
of the LOE are arranged in a spaced-apart relationship along two
perpendicular axes in said at least one plane.
[0021] The present invention provides a novel method for
fabricating the above-described LOE. Moreover, the method of the
invention is advantageous for mass production of such LOEs, as is
provides a simple technique for concurrently manufacturing multiple
LOEs using any known suitable patterning technique(s).
[0022] Thus, according to another broad aspect of the invention, it
provides a method for fabrication of two or more light guide
optical elements (LOEs) configured as described above, the method
comprising:
[0023] preparing at least one patterned substrate, the patterned
substrate having an optically transparent planar body with a
surface thereof formed with a pattern of spaced apart, parallel,
light directing regions, which are arranged in an X-Z plane in a
spaced-apart relationship along one of X-axis and Z-axis with
optically transparent spacer regions between them;
[0024] enclosing said at least one patterned substrate between top
and bottom optically transparent substrates, thereby forming a
stack of multiple optically transparent layers stacked one on top
of the other along Y-axis, where the pattern of the spaced apart,
parallel, light directing regions is located at an interface
between the layers;
[0025] dicing said stack of multiple optically transparent layers
along a dicing plane intersecting with the X-Z plane and forming a
predetermined angle with the X-Z plane, into a predetermined number
of slices spaced from one another along the X-axis, to thereby
define a plurality of bodies for the LOEs, each of said bodies
comprising the at least one light directing region which is fully
embedded in the LOE's body such that said at least one light
directing region is spaced from major surfaces of the LOE and forms
with said major surfaces said predetermined angle.
[0026] The method further comprises applying edge cutting to each
of said slices producing the LOE having the optically transparent
body having major surface and comprising the at least one light
directing surface embedded in the body spaced from the major
surfaces.
[0027] In some embodiments, where each of the LOEs to be fabricated
should include multiple light directing regions, more than one
patterned substrates are provided being placed one on top of the
other along the Y-axis and being all enclosed between the top and
bottom layers, such that the patterns of said patterned substrates
are located at interfaces between the adjacent layers and are
shifted with respect to one another along one of X-axis and Z-axis,
thereby forming said plurality of the LOEs, each LOE comprising an
inner pattern comprising two or more spaced-apart light directing
regions fully embedded in the body.
[0028] It should be noted that, in some embodiments, the shift
value is smaller than a minimal spacer/uncoated region between the
adjacent light directing regions in the layer.
[0029] The above shift of the patterns in the adjacent layers can
be achieved by properly applying the patterning process; or by
shifting the similarly patterned substrates with respect to one
another along X-axis.
[0030] The dimensions of the spacer regions and the dicing of the
stack into the slices define distance(s) of the light directing
region(s) from the major surfaces of the LOE. The two or more light
directing regions may include regions of different dimensions, as
well as may include regions having different optical properties
differently affecting the input light.
[0031] The patterned layers may be of the same or different
thicknesses.
[0032] As indicated above, the patterned substrate may be prepared
by any known suitable technique, e.g. a lithography process
(negative or positive patterning) creating the pattern of the
spaced apart, parallel, light directing regions spaced by optically
transparent spacer regions; or applying to a surface of the
optically transparent planar body a direct writing patterning
process.
[0033] It should be understood that, in some cases, an intermediate
structure formed by the above-described stack of multiple optically
transparent layers where one or more of the layers have the surface
pattern, can be produced, and supplied to a customer for further
slicing into LOE bodies, when needed.
[0034] The invention, in its yet further broad aspect provides such
an optical structure prepared for forming therefrom multiple LOE's
bodies. The optical structure is configured as a stack of multiple
optically transparent layers, wherein:
[0035] each of said optically transparent layers has a surface
pattern of parallel light directing regions which are arranged in
an X-Z plane in a spaced-apart relationship along at least X-axis
with optically transparent space regions between them;
[0036] the multiple layers are stacked one on top of the other
along Y-axis such that each of the surface patterns is located at
an interface between two adjacent layers and the patterns of said
layers are aligned with a shift of a predetermined value along one
of the X-axis and Z-axis,
[0037] thereby enabling dicing of the optical structure, along a
dicing plane intersecting with a X-Z plane and forming a
predetermined angle with the X-Z plane, into a predetermined number
of slices spaced along one of the X-axis and Z-axes, to produce a
plurality of bodies for the LOE elements, each of said bodies being
formed with an inner pattern comprising an array of spaced-apart,
parallel, light directing regions fully embedded in the LOE's body
and being inclined with respect to surfaces of the LOE body,
configured for major reflecting surfaces, with said predetermined
angle.
[0038] As indicated above, the multiple layers may include two or
more layers of different thicknesses.
[0039] The light directing regions of the pattern may be arranged
in spaced-apart relationship along both the X-axis and Z-axis.
[0040] The invention also provides a light guide optical element
(LOE) comprising an optically transparent body comprising major
surfaces and configured for guiding input light in a general
propagation direction through the body by total internal
reflections of light from said major surfaces, and carrying at
least one light directing surface configured for coupling said
input light out of the body towards one or more output directions
and being fully embedded in a volume of said body such that it is
spaced from the major surfaces, the LOE being manufactured by a
method comprising:
[0041] preparing at least one patterned substrate having an
optically transparent planar body with a surface thereof formed
with a pattern of spaced apart, parallel, light directing regions,
which are arranged in an X-Z plane in a spaced-apart relationship
along one of X-axis and Z-axis with optically transparent regions
of the substrate between them;
[0042] enclosing said at least one patterned substrate between top
and bottom optically transparent substrates, thereby forming a
stack of multiple optically transparent layers stacked one on top
of the other along Y-axis, where the pattern of the spaced apart,
parallel, light directing regions is located at an interface
between the layers;
[0043] dicing said stack of multiple optically transparent layers
along a dicing plane intersecting with an X-Z plane and forming a
predetermined angle with said X-Z plane, into a predetermined
number of slices spaced from one another along said one of the
X-axis and Z-axis, to thereby define a plurality of bodies for the
LOEs, each of said bodies comprising the at least one light
directing region which is fully embedded in the LOE's body
BRIEF DESCRIPTION OF THE DRAWINGS
[0044] In order to better understand the subject matter that is
disclosed herein and to exemplify how it may be carried out in
practice, embodiments will now be described, by way of non-limiting
examples only, with reference to the accompanying drawings, in
which:
[0045] FIG. 1A schematically illustrate the configuration and
operation of a convention planar light-guide optical element (LOE)
of the type to which the present invention relates;
[0046] FIGS. 1B and 1C show two known examples of the LOW
configuration aimed at solving the problem associated with the
conventional LOW configuration of FIG. 1A;
[0047] FIG. 2 shows schematically the configuration of the LOE
according to the present invention;
[0048] FIGS. 3A-3D show an example of a method of the invention for
fabrication of the multiple LOEs, each configured with a single
light directing region embedded in the LOE's body;
[0049] FIGS. 4A-4E show another example of a method of the
invention for fabrication of the multiple LOEs, each configured
with a plurality of the spaced-apart light directing regions
embedded in the LOE's body, by stacking multiple patterned
substrates where the regions in each substrate extend along the
Z-axis and are spaced along the X-axis, and the patterns in the
stacked substrates are shifted along the X-axis;
[0050] FIG. 4F exemplifies the LOE fabricated by the general method
of FIGS. 4A-D, but using different patterned layers, such that
multiple light directing surfaces in the LOE include light
directing surfaces having different dimensions and being
differently spaced from at least one of the major surfaces;
[0051] FIGS. 5A to 5G show yet another example of a method of the
invention for fabrication of the multiple LOEs, each configured
with a plurality of the spaced-apart light directing regions
embedded in the LOE's body, by stacking multiple patterned
substrates where the regions in each substrate extend along the
Z-axis and are spaced along the X-axis, and the patterns in the
stacked substrates are shifted along the Z-axis;
[0052] FIGS. 6A to 6F show yet further example of a method of the
invention for fabrication of the multiple LOEs, each configured
with a plurality of the spaced-apart light directing regions
embedded in the LOE's body, by stacking multiple patterned
substrates where the regions in each substrate extend along the
Z-axis and are spaced along both the X-axis and the Z-axis, and the
patterns in the stacked layers are shifted along the X-axis;
and
[0053] FIG. 7 illustrates a spectacles configured in which the
lenses incorporate the LOEs of the invention.
DETAILED DESCRIPTION OF EMBODIMENTS
[0054] As described above, FIG. 1A illustrates schematically the
configuration and operation (light propagation scheme) in a
conventional LOE device, and FIGS. 1B and 1C show two examples of
the improved LOE configuration providing that the light directing
surfaces are fully embedded in substrate of the LOE device, being
spaced from the major surface(s) thereof.
[0055] Reference is now made to FIG. 2 which schematically
illustrates a part of an LOE device 200 configured according to the
present invention. To facilitate understanding, the same reference
numbers are used for identifying components that are common in all
the examples of the invention and those of the known device
described above.
[0056] The LOE 200 includes an optically transparent body 20 which
has two major surfaces 26 and 28 and one or more light directing
surface 22. The LOE's is thus configured for guiding input light in
a general propagation direction D through the body by total
internal reflections of light from the major surfaces 26 and 28,
and interaction of the so-propagating light with the light
directing surface(s) 22 couples the light out of the body towards
one or more output directions. The LOE 200 is preferably configured
such that all of the light directing surface(s) 22 are fully
embedded in the volume of the body 20 being spaced (equally or not)
from the major surfaces. The LOE 200 is manufactured such that the
body 20 includes one or more internal interfaces, generally at 60,
where each internal interface extends between the major surfaces,
and where all the interfaces (in the simplest case there may be
only one such interface) are located in planes parallel to
that/those of the light directing surface(s) 22, and the light
directing surface(s) 22 is/are located in region(s), respectively,
such one or more interfaces 60.
[0057] The following are several examples of a fabrication method
of the invention for fabricating the LOE device of the invention.
The simplest example of concurrent manufacture of multiple bodies
for LOEs, where each LOEs includes a single light directing region,
is shown in FIGS. 3A-3D; and more practical examples for concurrent
manufacture of multiple LOE's bodies where each LOE includes an
array of two or more light directing surfaces 22 arranged in an X-Z
plane in a spaced-apart parallel relationship along one of the
X-axis and Z-axis (the light directing regions may be elongated
extending along the Z-axis) are described below with reference to
FIGS. 4A-4E, 5A-5G and 6A-6F.
[0058] As shown in FIG. 3A, a patterned substrate 70 is prepared.
The patterned substrate 70 has an optically transparent planar body
20 with at least one surface pattern 72A on at least one of its
surfaces 70A. It should be understood, although not specifically
shown, that the opposite surface 70B may also be provided with a
surface pattern. The pattern 72A is in the form of an array of
spaced apart, parallel, light directing regions 22 (generally at
least two such regions) spaced by optically transparent regions 74
of the substrate 20. Typically, the regions 22 and 74 are,
respectively, coated by desired light directing material (e.g. at
least partially reflective or diffractive) and transparent regions
(i.e., not configured to cause redirecting of light) which are
typically uncoated. The transparent regions are referred to herein
according to a preferred embodiment as "uncoated", but it should be
understood that this does not preclude implementations in which
various coatings or layers are present at the transparent regions
which, after bonding with suitable index-matched optical cement or
other optical bonding techniques, maintain the required
transparency of the transparent regions. The light directing
regions 22 in this example are elongated extending along the
Z-axis, and are arranged in a spaced-apart relationship along the
X-axis with optically transparent uncoated regions 74 between them.
The surface pattern 72A may be created using any known suitable
techniques, such as lithography (negative or positive), direct
writing, etc., following or preceding with an optical coating
process.
[0059] It should be noted, and will described more specifically
further below that the light directing regions 22 may be arranged
in a two-dimensional array, i.e. light directing regions may be
spaced apart along both the X- and Z-axes.
[0060] Then, the patterned substrate 70 is enclosed between
optically transparent layers 76 (or at least the patterned surface
70A is covered by such layer 76). Thus, a multi-layer stack 80 is
created, by gluing with an optical adhesive, including optically
transparent layers (substrates) 20, 76 stacked one on top of the
other along the Y-axis, where the pattern 72A of the light
directing regions 22 is located at an interface 50 between the
layers. As noted above, the configuration may be such that another
surface pattern is made on surface 70B and is thus located at an
interface between surface 70B and the other optically transparent
layer 76.
[0061] Then, a dicing/cutting is applied to the stack 80 (FIG. 3C)
along dicing planes 82 which intersect with the X-Z plane at
predetermined angle and pass through the optically transparent
uncoated regions 74. By this a plurality of LOE's bodies 20 are
fabricated--11 such bodies in the present example, only one of
which being shown in FIG. 3D. Each such LOE has one light directing
region 22 fully embedded in the LOE's body 20 and forming said
angle with the major surfaces. As shown, such LOE has no internal
interfaces other than interface 50 which is located in a plane
parallel to the light directing surface 22 and said light directing
surface is located on a region of the interface 50 while being
spaced from the outer surfaces of the body 22.
[0062] These outer major surfaces may than be further processed by
the application of a various coatings including, but not limited
to, Hard Coating (HC), Anti-scratch coating, super-hydrophobic
coating, anti-smudge coating, anti-bacterial and anti-fouling
coating, Anti-reflection coating, to create the major reflective
surfaces of the LOE. Methods for the creating these coatings may
include but are not limited to, liquid/solvent based coating such
as dip coating, spin coating, spray-coating, die coating, capillary
coating, roll coating, curtain/knife coating, bar-coating, or
various printing technique, and may further include a curing step
(e.g. UV/Electron beam/Thermal curing) and an additional polishing
step. Alternatively, dry coatings like evaporation or sputtering of
optical coatings might be applied. It should also be noted,
although not specifically shown here, that an edge cutting process
can be applied to each body resulting from the dicing process,
thereby producing the LOE of the desired configuration to guiding
input light in a general propagation direction by total internal
reflections from the major surfaces and coupling light out of the
LOE by interaction with the light directing surface.
[0063] As mentioned above, the method of the invention can
advantageously be used for concurrent manufacture of a large number
of LOEs, each including an array of light directing surfaces. One
of such method is exemplified in FIGS. 4A-4E. In this example, the
method starts from preparation of the patterned substrates 70 (FIG.
4A) generally similar to the substrate of FIG. 3A. The substrates
are prepared using any known suitable patterning technique.
[0064] The patterned substrates 70 are optically bonded along the
Y-axis with an optical adhesive in an aligned manner one on top of
the other (FIG. 4B), and may be enclosed between top and bottom
optically transparent layers or only uppermost patterned surface
may be covered by an optically transparent layer. By this, a
multi-layer stack 80 is fabricated. In such stack 80, the patterns
72 are located at interfaces between the adjacent layers. Also, in
such stack, the patterns 72 located in different planes are shifted
with respect to one another along the X-axis with a predetermined
shift value .DELTA.x. The shift value .DELTA.x is smaller than the
minimal X-dimension, X.sub.uncoat, of the uncoated optically
transparent region 74 between the adjacent light directing regions
22 in the layer. Such shifted-patterns' configuration can be
obtained by either preparing the patterned layers with the required
shift of the patterns, or by stacking the similarly patterned
layers with the required lateral shift.
[0065] Then, the above-described dicing/cutting process is applied
to the multi-layer stack 80 (FIGS. 4C and 4D) along dicing planes
82 which intersect with the X-Z plane forming a predetermined angle
.theta. with the X-Z plane (as shown in FIG. 4D) and pass through
the spacer regions 74 in all the patterned layers. This process
results in the multiple LOE's bodies, each configured as shown in
FIG. 4E, being formed with the multiple light directing regions 22
all fully embedded in the body 20 such that they are spaced from
the major surfaces and are oriented with the angle .theta. with
respect to the major surfaces. Also, the edge cutting process can
be applied, either to the entire stack 80, or separately to each
LOE body resulting from the dicing process.
[0066] It should be understood that the dimensions of the
spacer/uncoated regions 74 between the light directing regions 22,
as well as the parameters of the dicing applied to the stack,
define distance(s) of the light directing regions 22 from the major
surfaces of the LOE. As exemplified in FIG. 4F, the configuration
may be such that the light directing regions 22 in the LOE 20
include regions of the same or different dimensions, as well as
regions that are equally or differently spaced from the major
surfaces.
[0067] FIGS. 5A to 5G show another example of a method of the
invention for fabrication of the multiple LOEs, each having an
array of light directing regions. First, multiple patterned
substrates are prepared, one such patterned substrate 70 being
shown in FIG. 5A. The patterned substrate has an optically
transparent planar body 20 with a surface pattern 72A on at least
one surfaces 70A. As mentioned above, the opposite surface of the
substrate may also be provided with a surface pattern. The pattern
72A is in the form of two or more spaced apart, parallel, light
directing regions 22 (regions coated with the required light
redirecting material, such as reflective, partially reflective, or
diffractive material) spaced by optically transparent (uncoated)
regions 74 along the X-axis. In this example, the light directing
22 regions are elongated (lines) extend along the Z-axis. The
surface pattern 72A may be created using any known suitable
techniques, such as lithography (negative or positive), direct
writing, etc., following or preceding with an optical coating
process.
[0068] Multiple patterned substrates 70 are prepared to be enclosed
between top and bottom optically transparent layers/plates 76 (FIG.
5B). The patterned substrates 70 are then stacked using an optical
adhesive in an aligned manner one on top of the other along the
Y-axis (FIG. 5C), and enclosed between the top and bottom optically
transparent unpatterned plates 76 (or only the uppermost patterned
surface may be covered by an optically transparent plate 76). By
this, a multi-layer stack 80 is fabricated. In such stack 80, the
patterns 72 (light directing regions) are located at the interfaces
50 between the adjacent layers. Also, in such stack 80, the
substrates are shifted with respect to one another along the Z-axis
with a predetermined shift value .DELTA.z.
[0069] A dicing/cutting process being applied to the multi-layer
stack 80 is shown in FIG. 5D. As shown, the dicing planes 82
intersect with the X-Z plane forming a predetermined angle with the
X-Z plane (as described above with reference to FIG. 4D). This
process results in multiple LOE substrates--one such substrate 20
being shown in FIG. 5E. This substrate has two arrays 78A and 78B
of light directing regions embedded therein (generally, two or more
arrays, depending on the pattern in each initial substrate 70),
where the light directing regions in the array are arranged in a
spaced-apart relationship along the Z-axis, and the two arrays are
arranged with a space 84 between them along the X-axis. A further
dicing/cutting stage may optionally be applied to the space region
84 in such multi-array substrate (FIG. 5F), in order to obtain two
LOE bodies 20A and 20B, containing respectively arrays 78A and 78B
of the embedded light directing regions. In implementations of the
present invention in which dicing is performed on two non-parallel
planes, at least one of the dicing planes preferably passes through
the transparent regions so as not to intersect the light directing
regions so that the light directing regions are spaced inwards from
the outer surface in the corresponding dimension of the LOE. In the
present example, dicing planes 82 do intersect embedded light
directing regions 78A and 78B, but the dicing plane of FIG. 5F does
not. In this case, the light directing regions are not "fully
embedded", as described in the following embodiments, but are
inwardly spaced from the external surfaces of the LOE in at least
one dimension. As shown in FIG. 5G, each of the so-obtained LOE's
substrates/bodies further undergoes edge cutting and polishing. The
light directing regions 22 are located within interfaces 50
oriented at the angle .theta. with respect to major surface 26 and
28, and regions 22 are appropriately spaced from the major
surfaces.
[0070] It should be understood that the cutting process of FIG. 5F
can alternatively be applied to the entire stack 80 of FIG. 5C,
prior to the dicing process exemplified in FIG. 5D (i.e. dicing
along planes 82). In this case, the dicing of FIG. 5D would be
applied twice, separately to the each of two so-obtained
single-array stacks.
[0071] Reference is now made to FIGS. 6A to 6F showing yet further
example of a method of the invention for concurrent fabrication of
the multiple LOEs, each with multiple light directing regions. This
example is actually an alternative to that of FIGS. 5A-5G.
[0072] FIG. 6A shows one of a multiple patterned substrates 70.
However, in this example, a patterned surface (generally, at least
one surface) of the substrate 70 has a pattern in the form of a
two-dimensional array of light directing regions arranged in a
spaced-apart relationship along both the X-axis and the Z-axis. As
described above, the light directing regions are coated by desired
light directing material and are spaced by uncoated regions of the
substrate. Thus, the pattern may be described as being formed by
two arrays 72A and 72B of regions 22, where the arrays are spaced
along the Z-axis, and the regions 22 of each array are spaced-apart
along the X-axis.
[0073] Multiple patterned substrates 70 are prepared and put one on
top of the other such that the patterns of different substrates are
shifted with respect to one another along the X-axis a
predetermined shift value .DELTA.x, as shown in FIG. 6B. The shift
value .DELTA.x is smaller than the minimal X-dimension,
X.sub.uncoat, of the uncoated optically transparent region 74
between the adjacent light directing regions 22 in the layer. It
should be understood that in order to obtain such shift between the
patterns, either the initially prepared substrates have shifted
patterns, or the similarly patterned substrates are stacked with
such shift, or both techniques are used.
[0074] The patterned substrates are optically bonded with an
optical adhesive in an aligned manner one on top of the other to
form a stack 80 (FIG. 6C), and may be enclosed between top and
bottom optically transparent layers 76 (or only covered by the
uppermost layer). In such stack 80, the patterns (light directing
regions 22) are located at interfaces 50 between the adjacent
layers/substrates.
[0075] A dicing/cutting process, similar to that described above
with respect to FIGS. 3C and 4C, is applied to the multi-layer
stack 80 (FIG. 6D) along dicing planes 82 which intersect with the
X-Z plane forming a predetermined angle .theta. therewith as
described above. The resulting LOE body 20, being one of the
multiple bodies, is shown in FIG. 6E, and after the edge cutting
and polishing process--is shown in FIG. 6F. As described above, in
this example, the dicing/cutting along the X-axis in the space
between the two arrays, might be first applied to the stack 80 and
then the dicing along planes 82 may be applied to each of the
resulting half-stacks. Each LOE body 20 has multiple spaced-apart
parallel light directing regions all fully embedded in the body
such that they are spaced (equally or not) from the surfaces 26 and
28 that are to serve as major surfaces.
[0076] It should be understood that the LOE produced by the methods
of the invention (FIGS. 3D, 4E, 5G and 6F) has no internal
interfaces other than interfaces 50 which are located in a plane
parallel to the light directing surface 22 and said light directing
surfaces are located in regions of the interfaces 50, while being
spaced from the external surfaces of the body 22 in at least one
dimension, and in particularly preferred cases, being spaced from
the surfaces to be used as the major reflective surfaces of body
22.
[0077] FIG. 7 exemplifies how the structure (LOE) of the invention
can be incorporated in spectacles. Each lens in the spectacles is
formed as or carries the LOE attached thereto, and, when used
together with a virtual image source, the light directing surfaces
directs virtual image light towards the wearer's eye.
* * * * *